We still seek to identify the substance(s) in urine and serum which inhibit crystallization of calcium salts, either alone, additively or synergistically, when tested in solutions with a nidus present--either ricketic cartilage or phosphate prepared tendon. An additional recent finding may be highly significant-- that the total inhibitor strength of a urine as passed is sharply altered if taken to pH1 or pH12 prior to testing at 7.4. Interestingly, artificial urine, made up of some 30 known constituents, is also subject to alterations in inhibitory potential by pH changes, though not so great, either as whole urine untreated or after pH treatment. It is believed that identification of inhibitors of calcification is of great importance, not only in the problem of nephrolithiasis, but in many body physiological processes.